For a vehicle, there is widely used a planetary gear type step-variable transmission which uses a plurality of planetary gear sets and coupling devices such as clutches and brakes for connecting elements of the planetary gear sets, for selectively establishing a plurality of predetermined speed ratios or gear positions. Patent Document 1 discloses an example of a step-variable transmission in the form of an automatic transmission for a front-engine front-drive vehicle (hereinafter referred to as “FF vehicle”) or a rear-engine rear drive vehicle (hereinafter referred to as “RR vehicle”). This automatic transmission uses three planetary gear sets to provide six forward-drive gear positions.                [Patent Document 1] JP-2000-161450 A        [Patent Document 2] JP-2001-182785 A        [Patent Document 3] JP-2002-323098 A        